Large flat bed printers are used for printing on rigid and semi-rigid substrates. A typical flat bed printer has a print head array arranged to move in one direction and a flat bed arranged to move in a direction perpendicular to the direction of movement of the print head. The flat bed might typically have a dimension of 3.2 m×1.65 m and a vacuum is delivered to it to hold the substrate in position during printing. A problem associated with this kind of printer is the need to maintain a constant vacuum over such a large area. The vacuum is required to firmly hold the substrate in position while the flat bed travels a typical distance of 7 m with a speed of approximately 2.5 m.s−1 and an acceleration of up to 0.8 m.s−2.
In order to provide a firm hold to substrates such as cardboard, Kappa® and vinyl panels a continuous and stable vacuum is typically required of approximately −0.3 bar with a flow rate of 450 m3.−1. The vacuum is typically supplied to the flat bed from a vacuum pump using large diameter tubing which is relatively long and which must unfurl as the flat bed travels relative to the vacuum pump. A problem with using such tubing is that it is heavy and significantly increases the flat bed mass. The tubing also causes friction due to the requirement to continuously move the flat bed. A powerful drive must typically be used to operate the flat bed, which is expensive and requires a large amount of energy. Such a powerful drive may also be noisy. The need for the tubing to travel with the flat bed also produces undesirable vibrations which can degrade the print quality. There are also maintenance problems with the large diameter tubing which may crack or split. Overall a lighter bed is more desirable due to the above mentioned problems.